Oscillograph



R. H. GEORGE 6% h, mwm

R. H. GEORGE 2,086,546

July 13, 1937.

OSCILLOGRAPH Filed Sept. 14, 1929 8 Sheets-Sheet 4 5&2772565 R. H. GEORGE July 13, 1937.

OSCILLOGRAPH Filed Sept. 14, 1929 8 Sheets-Sheet 5 July 13, 1937. R. H. GEORGE OSCILLOGRAPH Filed Sept. 14, 1929 HIGH VOLTAGE LINE 8 Sheets-Sheet 7 JJ' JJ T0 FILAMENT SUPPLY 7'0 T'IMl/VG CIRCUIT TD I-ILAMENT SUPPLY J60 mam! 0 w Tin/N6 :5 6 puma/r 1F Jag/09142] R. H. GEORGE July 13, 1937.

OSCILLOGRAPH Filed Sept. 14, 1929 8 Sheets-Sheet 8 E 539 @QREMEK j m w v Q. m/

M I y I J; I I I I I I I I I Patented July 13, 1937 OSCILLOGRAPH Application September 14, 1929, Serial No. 392,591

36 Claims.

This invention relates to oscillographs and methods of operating the same and has particular relation to cathode-ray oscillographs and systems of electrical connections therefor, whereby transient electrical phenomena and the like may be accurately and efiiciently recorded or observed.

A very urgent demand for further knowledge of lightning and other transient phenomena, and other high-frequency electrical phenomena in general, has resulted in the development of three general types of cathode-ray oscillographs for such investigations. These types are the highvoltage cold-cathode type, the low-voltage hot cathode type and the medium-voltage hot-cathode type.

The cold-cathode type of oscillograph employs a gaseous discharge which requires from 30,000 to 90,000 volts to produce the cathode ray or beam. Because of the high velocity and resultant penetrating power of the electrons constituting the beam, this type of instrument has a high sensitivity with respect to the photographic recording of the movements of the cathode ray or beam, but has a low sensitivity with respect to the deflection of the beam to produce the movement thereof indicating the characteristics of the phenomena to be recorded or observed. It is also dimcult to control the intense discharge of this type of instrument for more than a fraction of a second, and, therefore, instruments of this type are best adapted for recording phe-.- nomena of very short duration only. The cathode ray or beam is also quite sensitive to gas pressure, and is slow to get into operation, which is a material factor in the recording of lighting surges, for example, the time of occurrence of which cannot be predetermined.

The low-voltage hot-cathode type of instrument, utilizing 300 to 1,000 volts in its operation, has the advantage that the cathode ray or beam can be focused to a well-defined spot of high intensity on the photographic plate or viewing screen. The beam is also very sensitive to deflecting fields and may be maintained for an indefinite period of time. This type of instru- .nent has the disadvantage, however, that its photographic sensitivity for recording purposes is extremely low.

The medium-voltage hot-cathode type of oscillograph, operated on voltages of the magnitude of 1,000 to 20,000 volts, has the advantages of increased photographic sensitivity and in the fact that the beam may be maintained continuously. The inherent decrease in deflectional sensitivity caused by the increase in voltage necessitates the employment of special means for focusing the beam and for creating the deflecting fields in its path of travel. Other difficulties which have been heretofore encountered in the utilization of this type of instrument are the removal of the oxide coat from the hot cathode or filament by positive-ion bombardment and the formation of a gas discharge which produces a large beam sur-- rounding the main beam or cathode ray.

The primary object of the present invention is to produce a general-purpose cathode-ray oscillograph of the hot-cathode type, which may have sufficient flexibility to be operated over a wide range of voltages and which may still produce an intense, well-focused beam of high photographic and defiectional sensitivity, combining, as far as possible, the desirable qualities of previous types of such instruments without detracting from the simplicity and reliability of operation heretofore attained.

It is also an object of the present invention to produce an instrument of the above-indicated character that will be robust and reliable in order that it may be readily adaptable for portable use without afiecting the accuracy and emciency of its operation.

A further object of the invention is to provide an instrument of the above-indicated character and systems for controlling the operation of the same, whereby phenomena of extremely short duration and occurring at times which cannot be predicted may be automatically, fully, and accurately observed or recorded.

The oscillograph constituting the invention has been designed and developed with a particular view to gaining the necessary photographic sensitivity through the use of a high-intensity cathode ray or beam at a minimum beam voltage. One of the principal problems, then, has been to devise satisfactory means for producing and focusing a high-intensity beam over a sufficient range of beam voltages to insure the necessary photographic sensitivity. The solution of this problem constitutes one of the major advantages of the invention.

Other objects and advantages of the invention will appear from a consideration of the follow ing detailed description in conjunction with the accompanying drawings illustrating a preferred embodiment of the invention. In these drawings:

v Figure 1 is a side elevational view of an assembled instrument constructed in accordance with the invention;

Fig. 2 is a front elevational view of the instrument shown in Fig. 1;

Fig. 3 is an enlarged fragmentary vertical sectional view taken on the line 38 of'Fig. 2;

Fig. 4 is a still further enlarged fragmentary vertical sectional view taken von the line d-fl of Fig. 3;

Fig. 5 is a horizontal sectional view'taken on the line 55 of Fig. 4;

Fig. 6 is an enlarged horizontal sectional view taken on the line 66 of Fig. 3;

Fig. 7 is an enlarged fragmentary vertical sectional view taken on the line 1-1 of Fig. 2;

Fig. 8 is an enlarged fragmentary vertical sectional view taken on the line 8-8 of Fig. 2;

Fig. 9 is a fragmentary vertical sectional view taken on the line 9-9 of Fig. 8;

Fig. 10 is a view, partly in side elevation and partly in central vertical section, of a particular type of electron tube that is preferably utilized in automatically controlling certain circuits for imparting a timing motion to a cathode ray or beam in an oscillograph constructed in accordance with the present invention; V

Fig. 11 is a horizontal sectional view taken on the line ll-ll of Fig. 10;

Fig. 12.is a diagrammatic view showing certain parts of the instrument considerably enlarged in vertical section on the same line as that on which Fig. 4 is taken and illustrating the natur'eof an electrostatic field established between certain of the parts for a purpose hereinafter specified;

Fig. 13 is a diagrammatic representation of certain electrical apparatus and circuits, whereby an oscillograph constructed in accordance with the invention may be arranged and connected to be brought into operation automatically upon the occurrence of transient phenomena which it is desired to record;

Fig. 14 is a diagrammatic representation of a modified system of circuit connections for the same purpose as the system shown in Fig. 13;

Fig. 15 is a diagrammatic representation of the phase relations of the various characteristics of the circuits shown in Figs. 13 and 14; and

Fig. 16 is a diagrammatic representation of certain electricalapparatus and circuits for imparting a timing motion to a cathode ray or beam in an os'cillograph constructed in accordance with the present invention, in a preferred manner.

The general elements of construction of the preferred embodiment of the invention are best shown in Figs. 1 and 2 of the drawings, in which it may be seen that a base plate 2| supports a horizontally extending cylindrical chamber 22. From the upper portion of the chamber 22 a tapered casing portion 23 extends upwardly to support a vertically extending casing portion 25,

the exterior of which is shown as being octagonal in cross section. To the upper extremity of the casing portion 24, a cylindrical casing portion 25 of insulating material is secured by means of a sleeve nut 26, and to the upper extremity of this casing portion 25 another cylindrical casing portion 21 is, in turn, secured by means of a sleeve nut 28. The upper extremity of this casing portion 21 is closed by an insulating cap member 29 that is secured in position by a sleeve nut 30.

members, such as insulating side plates 3| and vertical rods 32, which latter are partly of metal and partly of insulating material, as will appear hereinafter. These side plates and rods are supthe main casing of the instrument in a manner which-will be better understood upon reference to the detailed drawings and description thereof hereinafter.

The entire casing of the apparatus is adapted to be evacuated to facilitate the desired operation of the instrument and for this purpose a connection 36 is provided to extend to a suitable vacuum pump. The connection 36 is connected to the casing portions 22 and 23 through a drying chamber 31 and two pipe or conduit sections 38 and 39. One end of the drying chamber 31 is provided with a removable cap 40 to permit the insertion ofacontainer of drying material, such as a suitable hygroscopic chemical or the like, and the opposite end of this chamber is provided with a valve 4| for controlling the connection of the instrument casing to the vacuum pump through the connection 36. The latter connection preferably includes a second valve 62 for connecting the interior of the instrument casing to the atmosphere in order to break the vacuum within said casing when desired.

One end of the cylindrical portion 22 of the casing is provided with a hinged door 23 adapted to be tightly sealed by a suitable gasket or otherwise and to be opened by means of a handle 66. Since this door is held very tightly closed by the external atmospheric pressure when the interior of the casing is evacuated, it is also desirable to provide a releasing screw 65, which extends through a screw threaded hole in a projecting portion of the end wall of the casing portion 22 and abuts against the inner surface of the door 43 near the periphery thereof. A pin 66 extends through a hole in the head of the screw 55, in order that this screw may be turned manually to effect a slight opening of the door 43 when the vacuum within the casing has been broken.

When the door 43 is thus moved a slight distance it may be readily opened by means of the handle 44.

be noted here, however, that a cover 41a prevents light from entering the casing through said window when the latter is not in use.

Referring now to Figs. 3, 4, 5, and 6, it will be seen that the uppermost cylindrical casing portion 21, which is preferably of brass or other suitable metal, is externally screw threaded near its upper extremity to receive the internally screw threaded portion of the flanged sleeve 30. The upper portion of this sleeve comprises an inwardly extending flanged portion 300, which ex- :tends over a shoulder portion 29a of the insulating cap member 29. The bottom surface of the cap member 29 is provided with an annular groove fitting over a reduced diameter portion 210. of the metallic casing portion 2.! at the upper extremity thereof. An annular; washer or gasket 88 is disposed within the annular groove in the bottom of the cap member 29 and is forced firmly against the top surface of the reduced diameter portion 21a by the firm application of the flanged sleeve 30 to the threaded portion of the member 21. The washer or gasket 48 is preferably made 5 of rubber and with the construction disclosed forms a perfectly air-tight connection between the casing portion 21 and the cap member 29 to facilitate the evacuation of the casing.

The upper portion of the cap member 29 is bored to receive a plug member 49 that is also of insulating material in snugly fitting relation. A rubber gasket 50 is placed beneath the plug member 49 and both the plug member and the gasket are perforated to accommodate two conducting rods 5| which extend downwardly through the cap member 29 as well as upwardly through 'the plug member'49, the cap member 29 being similarly perforated for this purpose.

The rods 5| are provided with integral collar portions 5|a about midway of their length, and

these collar portions are disposed within counterbores in the cap member 29. of the collar portions 5| a are tapered to produce a frusto-conical surface corresponding to the angle of inclination of the bottoms of the counterbores in the cap member 29 and rubber gaskets 52 are disposed between the bottoms of the collar portions 5|a and the bottom surfaces of these counterbores.

30 The plug member 49, the gasket 50, the conductors 5|, and the gaskets 52 are maintained in assembled relation, as shown, by machine screws 53 extending through suitable holes in the plug member 49 and entering suitable threaded openings in the plug member 29. These screws are screwed tightly into position to hold the parts in firm engagement with each other whereby the rubber gaskets form an air-tight seal for the interior of the casing.

The lower extremities of the conductors 5| have connecting sleeves 54 suitably secured thereto, as by set-screws 55, and flexible conducting leads 56 are respectively soldered to or otherwise suitably electrically connected with the sleeves 54. The lower extremities of the flexible leads 56 are similarly connected to two connecting sleeves 51 which, in turn, are respectively secured by set-screws 58 to conductor rods 59 and 60. The rod 60 is soldered or otherwise suitably connected to a metallic locking sleeve 6| that is provided with external screw threads, as is also a metallic sleeve 62, to cooperate with corresponding internal screw threads in another metallic sleeve 63. The sleeve 63 is suitably secured within an insulating bushing 64 by means of nuts 65 and 66 respectively engaging external screw threads at the upper and lower extremities of said sleeve, and the sleeve 62 is adapted to be adjusted to any desired vertical position with respect to the sleeve 63 by reason of its screwthreaded engagement therewith, and to be locked in the desired position by means of the locking sleeve 6|, which thus acts as a lock-nut.

The nut 65 engages the top of a reduceddiameter portion 64a of the insulating bushing 64, while the nut 66 engages a shoulder 641) formed by an enlarged bore in the lower portion of said bushing. It will be seen that the vertical position of the sleeve 53 and parts carried thereby,

711 With respect to the insulating bushing 64, may

be adjusted by varying the positions of the nuts 65 and 66 on the screw-threaded portions of said sleeve.

The insulating bushing 64, in turn, is supported by a tubular metallic sleeve member 61 having a The under faces 1 free sliding fit with respect to the interior of the tubular casing portion 21. The bushing 64 fits snugly within the bore of the sleeve 61 and its lower extremity rests upon a shoulder formed by an inwardly extending flange or bottom portion 61a of the sleeve 61. An'annular securing nut -68 surrounds the reduced-diameter portion 64a at the top of the bushing 64 and is provided with external screw threads cooperating with internal screw threads in the upper portion of the bore of the sleeve 61. By screwing the nut 68 firmly into the'upper extremity of the sleeve 61,

. the bottom of this nut is caused to force the bushing 64 firmly down against the inwardly extending shoulder portion 61a of the sleeve 61 and the bushing 64 is thus firmly secured within the metallic sleeve 61.

The outer surface of the metallic sleeve 61 is provided with a plurality of longitudinally extending slots or grooves 61b to form a direct path for the passage of air between the portions of the casing 21 above and below the sleeve 61 and parts carried thereby. The sleeve 61 is thus provided with ample bearing surface for sliding movement within the casing portion 21 during insertion and removal of said sleeve, without obstructing the passage of gases between the diiferent parts of the casing.

The bottom portion 61a of the sleeve 61 rests upon the top of a substantially bell-shaped but open-topped metallic member 69 as a support. The member 69 comprises a perforated integral collar portion 69a that is externally screwthreaded for the purpose of securing the same within the lower extremity of the casing portion 21, which is internally screw-threaded to receive the same. The perforations in the collar portion 69a of the member 69 are provided for the same purpose as the grooves 61b in the outer surface of the metallic sleeve 61, that is, to permit the free passage of gases between the various portions of the interior of the casing. The bottom portion 61a of the sleeve 61 is likewise perforated, as at 610, to connect the open space within the sleeve with the remainder of the casing.

The bottom of the sleeve 61 is closed by a plate or disc 19 having a tapered central aperture 19a therein for a. purpose hereinafter specified. While the bottom wall of the casing 61 may, if desired, be integrally formed and perforated at 61c and 10a, it is preferable that provision be made for accommodating removable plates or discs 10 as shown, in order that such plates or discs having apertures 10a of different sizes or formations may be interchangeably utilized to obtain the best possible results in operation of the instrument.

An insulating bushing 1| is secured within the bore of the metallic sleeve 62 by means of an externally screw threaded annular nut 12 cooperating with corresponding screw threads on the inside of the bore of the sleeve 62. The bottom of the bushing 1| is beveled to bear against a similarly beveled inwardly extending flange portion 62a of the sleeve 62 whereby the bottom of the bushing 1| is supported. The bushing 1| supports the conductor rod 59 which extends in snugly fitting relation through the bore of said bushing and which is provided with an integral collar portion 59a. bearing against the bottom of said bushing.

The portion of the conductor 59 immediately above the upper surface of the bushing 1| is screw-threaded to cooperate with an internally screw-threaded nut 13 which extends within the bore of the annular securing nut I2 and in spaced relation thereto. The bottom of the securing nut 13 thus bears against the top of the bushing H and when this nut is tightened it holds the conductor rod 58 securely within said bushing and in insulated relation to the metallic sleevesfii, 62 and 88.-

A ribbon-type filament M is supported within the metallic sleeve 63 and near the lower extremity thereof by two lead wires 15 and iii to which the opposite extremities of said filament are respectively connected and which, in turn, are respectively connected to the metallic sleeve =82 andv the conductor rod 59. The lead wires 18 and 18 are preferably supported with respect I to each other by a glass bead 'Ii near the lower rods 5! extending upwardly through the cap member 29 of the casing, and that the end of the filament which is connected to the lead wire 15 is electrically connected to the metallic sleeve 63 through the sleeve 62. It is preferable in some cases to have both of the filament leads insulated from the sleeve 63, in which case it will be readily understood that the conductor 60, instead of being connected to the sleeve 62 as shown, will extend downwardly through the in sulating bushing H in a manner similar to that in which the conductor 69 so extends, as herein shown and described.

The bottom of the sleeve $3 is internally screwthreaded to receive a similarly screw-threaded cap member it having a central aperture 78a therein in alignment with the aperture 10a in the plate or disc 70 closing the bottom of the sleeve 61. These two apertures are also in alignment with the filament id (which, however, is wider than said apertures), and are provided to permit the passage of electrons emitted from said filament in the desired downward direction. This filament is preferably provided with an oxide coating to facilitate such electron emission in a manner well mown in the art. This oxide coating is preferably applied to the filament on .the bottom surface only thereof, since it is desired that electrons be emitted only in a downward direction. It is for the purpose of preventing the emission of electrons in other directions that the filament is enclosed by the metallic sleeve 83 and the cap closure 88, which constitute an eflective filament shield.

The lower portion of the sleeve 63 is perforated, as at 8%, to facilitate the complete evacuation of the open space within said sleeve, thus insuring the complete removal of any gases that may be given oil? by the filament M when it is heated. Since the insulating bushing 66 extends downwardly around the lower extremity of the sleeve 83 for a substantial distance below the level of the perforations 63a; theemission of electrons through these perforations is substantially prevented.

It will be noted that the filament 76, its shield 83 and theplate or disc 10 constituting the top of the negative electrode 69 are assembled into a compact unit carried by the sleeve 61, which unit is readily removable from and replaceable in the casing portion 21 and which simply rests upon the top of, the member 69. The only connections to this unit are made through the flexible conducting leads 56, which are readily detachable when it is desired to rempve 9; replace the unit. This unit is designated as the electron gun", because it comprises the means for establishing the cathode ray or electron stream and for. initially focusing and accelerating the same. This initial focusing and accelerating effect can be regulated as desired by adjusting the spacing between the filament M and the plate 18 and between the plate I8 and the plate F0, or the bottom of the member 51.

The lower extremity of the casing portion 21 comprises an integral collar portion 21b that is adapted to be engaged by an inwardly extending flange portion 28a of the securing sleeve 28. An annular groove is provided in the bottom edge of the casing portion 21 and a reduced diameter portion 250. of the insulating casing portion 25 extends in snugly fitting relation into this groove and abuts against a rubber gasket or washer 19 to form an air-tight connection between the casing portions 25 and 21. These two casing portions are securely held in their respective positions by the securing sleeve 28, which is internally screw-threaded to cooperate with corresponding external screw-threads at the upper extremity of the casing portion 25.

As will hereinafter appear, the bell-shaped metallic member 69 constitutes a negative electrode for the establishment of an electrostatic field in the path of travel of the electrons emitted from the filament M. A cooperating positive electrode is provided in the form of a hollow cylindrical member 80, the upper extremity of which is of substantially smaller diameter than the internal diameter of the member 69. The upper extremity of the positive electrode is closed by a metallic cap member 8! having an annular protruding portion 8ia on the bottom thereof fitting snugly within the bore of the electrode 80. The cap member Bi has a central aperture Bib therethrough in vertical alignment with the apertures 70a and 18a and the filament Id to accommodate the electron jet or beam emitted downwardly from the filament 14. The aperture 8Ib is enlarged conically in a downward direction, as shown, thus forming a sharp edge at the top of the member 8! and preventing reflection of electrons from the walls of said aperture.

Referring now to Fig. 7, it will be seen that the positive electrode 80 is supported by a tubular member 82 into which a reduced-diameter portion 8011 at the lower extremity of said electrode 80 snugly fits, the shoulder formed by the upper extremity of this reduced diameter portion resting upon the top of the tubular member 82. The member 82 is slidably fitted within a tubular metallic casing portion 83 that is suitably secured to the upper extremity of the metallic casing portion 26, as by soldering, brazing, or the like. The outer surface of the tubular member 82 is provided with a plurality of longitudinal slots or grooves 821; in a similar manner and for the same purpose that the grooves 67b are provided in the outer surface of the metallic sleeve member 61 as heretofore described.

A rack 84! is provided on one side of one of the grooves 82a and is adapted to cooperate with a pinion 85 secured to or forming an integral part of a shaft 86 extending outwardly through an aperture in the tubular casing portion 83. A sealing gland or joint is provided around the shaft 86 to maintain an air-tight seal around said shaft. This gland or joint comprises a substantially cylindrical hollow casing portion 81 having its inner extremity fitted and brazed or welded into a counterbore in the outer surface of the casing portion 83, which counterbore is coaxial with the aperture in said casing portion through which the shaft 96 extends. The bore" of the member 81 is restricted at the inner extremity,

of said member to a diameter similar to that of the aperture in the member 83, which is just large enough to permit the shaft 86 to extend therethrough in freely rotatable relation. A mass of packing material 91a is disposed within the gland casing 81 around the shaft 86 and is held in place between the opposed concave surfaces of the inner end portion of the member 81 and a packing disc or washer 81b. The inside of the bore of the member 81 is screw-threaded to receive an externally threaded plug member 810 that is centrally apertured to surround the shaft 86 in closely fitting but free running relation and that is also provided with apertures 81d for the reception of a suitable wrench or other tool for forcing the disc or washer 812) against the packing material 81a. A bushing member 8112 that is also centrally apertured to receive the shaft 86 in closely fitting but free running relation comprises an externally screw-threaded reduced-diameter portion, that is screwed into the outer extremity of the gland casing 91 to prov de a journal forthe outer portion of the shaft 86, the casing 81 being of such length that when the parts are assembled a substantial amount of space remains between the member 810 and 81a and the casing 81 is provided with an aperture 81 on its upper side to permit this space to be filled with grease as indicated at 819. In this manner the oscillograph casing is made completely air-tight around the shaft 86, the grease 81g supplementing the packing 81a to form a perfect seal. lieved to be new and is claimed as a part of the invention disclosed herein.

The outer extremity of the shaft 86 is preferably provided with a knurled knob 88 which may be turned manually to adjust the vertical position of the slidable tubular member 82 and the positive electrode 80 that is carried thereby. Such manipulation of the knob 88 results in any desired change of the vertical position of the positive electrode 89 with respect to the negative electrode 69, this adjustment being provided for a purpose hereinafter explained.

The insulating casing portion 25 is secured in fixed relation to the tubular casing portion 83 by the securing sleeve 26, which comprises an inwardly extending flange portion 26a engaging the shoulder formed by an integral collar portion 251) near the lower extremity of the member 25. The lower portion of the securing sleeve 26 is internally screw-threaded to cooperate with corresponding external screw threads on the upper portion of the member 83 whereby the sleeve 26 may be screwed down to force the casing portion 25 downwardly into tight engagement with the casing portion 83. For the purpose of providing an air-tight connection at this point, the member 83 is provided on its top surface with an annular groove into which a reduceddiameter portion 250 at the bottom of the casing portion 25 extends in snugly fitting relation and is forced against a rubber gasket or washer 89 in a manner similar to that described with respect to the air-tight joint between the cap member 29 and the casing portion 21 and between the .top of the casing portion 25 and the bottom of the casing portion 21.

The lowerportion of the member 83 is reduced in diameter to form a downwardly extending This type of vacuum seal is beportion 830 spaced inwardly from the inner wall of the casing portion 24 and having an annular groove 83b formed in its inner surface. A plurality of perforations 83c extend through the downwardly extending portion 83a of the member 83 to connect the interior of the casing portion 24 with the interior of the casing portion 25 through the annular groove 83b and the longitudinal grooves 82a in the outer surface of the member 82. The provision of these various grooves and perforations is also for the purpose of facilitating the evacuation of. the entire open space within the several portions of the casing, as in the case of the several grooves and perforations heretofore described,

The backs of two pairs of metallic plates 99 and 9i are secured. within the casing portion 24, to the inner extremities of rods 92 and 93 respectively, the two rods supporting each pair of plates having a common axis perpendicular to the axis of the rods supporting the other pair of plates. Each of the pairs of supporting rods 92 and 93 extends outwardly through sealing glands 94 and 95, respectively, which are packed and sealed with grease as in the case of the gland 81. The inner portions of the glands 94 and 95 are preferably of brass or other suitable metal suitably fitted and secured in apertures in the walls of the metallic casing portion 24, as by soldering, brazing, or the like.

The glands 94 and 95 are constructed to insulate the rods 92 and 93 from the oscillograph casing, as well as to provide a perfectly airtight seal therearound, and for this purpose they comprise outwardly extending portions 94a and 95a, respectively, of suitable molded insulating material, or the like (see also Figs. 1 and 2), within which adjusting nuts 96 and 91, respectively, are disposed to be freely rotatable but fixed against axial sliding movement. The adjusting nuts 98 and 91 are internally screwthreaded to cooperate with external screw threads 92a and 93a on the outer portions of the rods 92 and 93. respectively, whereby the spacing between each of the pairs of plates 99 and 9| may be varied by turning the nuts 96 and 91. In order to prevent rotation of the rods 92 and 93 while the nuts 96 and 91 are being adjusted, the,outer extremities of angularly bent wires 98 and 99 are secured to the outer extremities of the rods 92 and 93, respectively, and the inner extremities of these wires are secured to pins I00 and HH carried by the outwardly extending insulating portions 94a and 95a, respectively, of the sealing and insulating glands 94-and 95.

It will appear hereinafter that the cathode ray or beam emitted from the filament 14 and accelerated downwardly through the instrument will pass between the two plates of each of the pairs of plates 98 and 9|, and that these plates will be suitably electrically energized to cause the ray or beam to be deflected from its normal path. In order that only the main portion of the beam may be permitted to pass between the pairs of deflecting plates, a diaphragm I02, having a centrally located aperture l92a therein, is disposed at the lower extremity of the reduced diameter portion 83a of the member 83. This diaphragm I02 is supported upon an annular inwardly extending shoulderv portion 83d at the bottom of the reduced-diameter portion 83a and cooperates therewith to limit the downward movement of the vertically slidable member 82, which abuts against the upper, surface of the 'off any stray electron emission which may be caused by a positive ion bombardment of the negative electrode 69 or other causes.

An externally screw-threaded annular member, I03 is disposed at an intermediate point within the casing portion 23 between the two pairs of deflecting plates 90 and 9| and is held in position by cooperating screw threads provided in the inner surface of the casing portion 24, this casing portion being counter-bored, as at 24a, to permit the insertion of the member I03 from the bottom of said casing portion. This member I03 is provided for the purpose of supporting a metal plate (not shown) between the two sets of deflecting plates 90 and 9| where it is found necessary to utilize such a plate to prevent voltages from being induced on one pair of plates from the other. The reason for not showing this plate and describing the same more fully is that it is not required for normal operation of the instrument, although the latter, as well be seen, has been designed to accommodate such extraordinary requirements.

The lower extremity of the casing portion 24 extends into an annular groove in the upper surface of a metallic collar member I03 and is suitably secured thereto by soldering, brazing, or the like. The lower surfaceof the member I04 comprises a downwardly extending annular portion I04a which extends in snugly fitting relation into an annular groove in the upper surface of a member I05. which constitutes the supporting base of the upper parts of the in strument. A rubber sealing gasket I06 is placed in the bottom of the groove in the upper surface of the member I05 and the bottom of the annular projecting portion I040. of the member I04 is forced against this gasket by a securing nut I01 having an inwardly extending flange portion I'Ia. at its upper extremity engaging the shoulder formed by the top of the collar member I04. The securing nut I0! is internally screwthreaded to cooperate with corresponding external screw threads on the member I and the outer surface of the member I01 is suitably knurled, as at I0'Ib, whereby it may be firmly screwed down onto the member I05 to make an air-tight connection between the members I00 and I05, as in the case of the similar air-tight connections heretofore described.

The lower extremity of the member I05 comprises an integral outwardly extending annular flange portion I05a upon which the bottom plate 33 is adapted to rest, this plate being centrally apertured so that it may be freely passed over the screw-threaded portion of the member I05. A securing nut I08 which also screw-threadedly engages the externally screwthreaded portion of the member I05 is adapted to be screwed down against the upper surface of' the plate 33 to maintain the same securely in its normal position as indicated.

It will be seen that the bottom plate 33 is thus firmly supported by the casing of the instrument and that this plate carries the insulating side plates 3| which, in turn, support the intermediate plate 34 that is centrally apertured to pass over the upper extremity of the casing portion 20. The bottom plate 33 also has secured thereto, as by securing nuts I09, the lower extremities of the rods 32, to the upper extremities of which the top insulating plate 35 is secured, as by nuts IIO. Each of the rods 32 is formed in two parts suitably joined together at the level of the intermediate plate 34. The lower portion 32a. of each of these rods, extending between the plates 33 and 30, is preferably of metal of square cross section, while the upper portion 32b, extending between the plates 30 and 35, is preferably of insulating material of circular cross section. The upper plate 35 is centrally apertured so that it may be passed over the sleeve nut 30 and the upper extremity of the casing portion ZI. It will also be noted that the insulating side walls 3I are suitably apertured to permit the extension of the rods 92 and 93 and the adjusting means therefor to a readily accessible position outside the space enclosed by these side walls.

The bottom of the member I05 is grooved to receive the upper extremity of the tapered casing portion 23 which is also of metal and is permanently secured to the member I05 in airtight relation by soldering or brazing, as indicated at III.

Referring now to Figs. 8 and 9, it will be seen that the lower extremity of the tapered casing portion 23 registers with an aperture in the top of the horizontally extending cylindrical casing portion 22 and is permanently and tightly secured to said casing portion 22 by soldering or brazing, as indicated at H2.

The ends of the casing portion 22 are respectively supported by vertical end plates H3 and H4 which are suitably secured to the ends of said casing portion by soldering or brazing to form perfectly air-tight joints. The end plate II 3 closes the left-hand end of the casing 22, as viewed in Fig. 8, and is apertured to receive the inner extremity of the pipe or conduit 38, the other extremity of which connects with the interior of the drying chamber 31. The pipe or conduit 39 similarly connects the drying chamber 31 with the casing portion 23, it being understood that both of the pipes or conduits 38 and 39 are brazed or soldered to the members to which they are connected at their respective extremities to form air-tight connections. The provision of the two pipes or conduits 38 and 39 insures complete and rapidevacuation of all parts of the casing without causing the air or other gases therefrom to encounter any unnecessary obstructions.

A tray or open container I I5 is disposed within the drying chamber 31 and is adapted to hold a quantity of phosphorous pentoxide or other hygroscopic material II 6 to prevent the passage of any moisture from the interior of the instrument (particularly from photographic films) into the pumping apparatus, where deleterious results would be caused thereby. The interior of the drying chamber 31 is connected through the valve M, as best shown in Fig. 9, with the connection 36 which extends to the vacuum pump (not shown), as previously stated. This valve is sealed to prevent any leakage of air into the instrument at this point, by means of grease supplied by a grease cup 310. to an interior annular groove 31b near the outer extremity of the member 31 surrounding the body portion of the valve AI.

A sealing and insulating gland H1 is also connected to the end plate I I3 for the purpose of permitting electrical conductors II 8 to be extended from the exterior of the easing into the interior thereof in electrically insulated and air-tight relation thereto. These conductors may be utilized for making connections to vacuum indicating lamps or devices and other circuits 'xwhich it may be found desirable to utilize within is apertured to permit the insertion and removal of the above mentioned film-winding mechanism, and this aperture is adapted to be closed and tightiyssealed by the hinged door 43, as

previously described.

The film-winding and carrying mechanism is constructed as a removable unit adapted to be supported by a frame I22, which is constituted by a piece of sheet metal forming a portion of a cylinder and apertured substantially in register with the bottom of the casing portion 22. The frame member I22 is located at the upper portion of the film-winding and supporting mechanism and is adapted to fit within the interior of the horizontally extending cylindrical casing portion 22 and to be supported upon rabbeed or grooved longitudinal rods I23 secured to the inher surface of this portion of the casing. With this manner of support it will be seen that the film mechanism may be slid into the casing portion 22 through the opening in the end wall II4 when the door 45 is open and that this mechanism will be accurately held in the desired position for the purpose of obtaining photographic records of the movements of the cathode ray, as will appear hereinafter.

Suspended from the supporting frame I22 are two end plates I24 and I25 between which a plurality of supporting rods I26 extend. The respective extremities of the rods I26 are secured to the end plates I 24 and I25 by screws I21, or other suitable means, and in this manner a rigid frame-work for the operative parts of the film mechanism is eventuated. Film-winding rolls or spools I28 and I29 are provided with suitable pintles journaled in the end plates I 24 and I25 and a photographic film I30 is adapted to be wound from one of these rolls or spool-s onto the other in the operation of the instrument. The film extends between the two rolls or spools I28 and I29 over two idler rolls I3I and I 32, which are alsojournaled in the end plates I24 and I 25.

Between the idler rolls I3! and I32 a horizontally extending plate or table I33 is disposed for supporting an intermediate portion of the film in register with the aperture through the top of the casing portion 22 and with the bottom of the casing portion 23. This plate or table I33 is rigidly secured at its opposite extremities to the end plates I24 and I25, and thus forms a solid support for the portion of the film I30 upon which the photographic records are made. Beneath the plate or table I33 a fixed tray I34 is disposed, this tray also being rigidly secured at its opposite extremities to the end plates I 24 and I25. This tray is adapted to support a removable tray I35 carrying a quantity of phosphorous pentoxide or other hygroscopic material I38 for absorbing any moisture which remains in the film I30 when the same is placed in the casing portion 22.

A resilient member I31 is supported by two of the rods I26 near the bottom of the end plates I24 and I25 and extends inwardly and upwardly past the film-winding rolls or spools I28 and I29. The upwardly extending portions of the member I3'I are comb-like to form a plurality of resilient prongs or fingers I3'Ia which bear firmly against the film I39 as it is wound upon or unwound from the rolls or spools I28 and I29. The pressure exerted upon the film I30 by these resilient prongs I3'Iav maintains the desired degree of tautness in the portion of the film between the two rolls or spools I28 and I29.

A handle member I38 is suitably secured to the end plate I25 to facilitate insertion and removal of the film mechanism into and out of the chamber 22. The right-hand extremity of the filmwinding roll or spool I29 is pivotally supported on a. pintle I39 which may be maintained in its operative position as illustrated by any suitable and well known means, and which may be retracted by means of a knurled knob I39a to permit removal and replacement of the spool I29. The right-hand extremity of the spool I28 is s milarly supported by 'a corresponding retractiblo pintle (not shown). The left-hand extremity of the roll or spool I28 is adapted to be engaged by su table turning prongs or fingers (not shown) connected to a knurled knob I40 (Fig. 1-), the s indle of which extends through the end wall II3 through an air-tight sealing gland Hi, to permit winding of the film from the roll or spool I99 onto the roll or spool :28 from the outside cf the casing of the instrument while the inside of said casing is evacuated to place the instrument in condition for operation.

By means of this mechanism, it will be understood that successive portions of the film I30 may be brought into register with the aperture in the top of the casing portion or film chamber 22, through which the cathode ray or beam enters said chamber. This operation may be performed without breaking the vacuum within the casing of the instrument, and thus a considerable number of photographic records may be made in a short time without extended intermediate delays, which would be occasioned if it were necessary to open the casing each time the film was to be changed, and therefore to reestablish the vacuum after each film change.

The purpose of providing the contact disc I20 and cooperating contact finger II9 will now appear. The disc I20 is carried by and secured to the left-hand extremity or pintle of the idler roll I32, as shown in Fig. 8, whereby this disc rotates with said idler roll. This roll is moved in unison with the movement of the film I30 by reason of the frictional engagement between the film and. roll, since the intermediate portion of the film between the two winding rolls I28 and I29 is always maintained in a taut condition, as previously described. Therefore, when the film is wound from the roll I29 onto the roll I28 by manipulation of the knurled knob I40, the contact disc I20 is rotated to a degree that is exactly proportional to the distance through which any given point of the film moves. The circumference of the roll I32 is such that one complete revolution thereof corresponds to a movement of the film I30 through a distance equal to the length of film utilized at each exposure thereof.

The initial exposure setting of the film is made with the contact-finger H9 in contact with the insulating insert I2I in the disc I20. when the film is moved toward the position which it is to occupy during its next exposure, the contact finger II9 contacts with the conducting portions of the disc I20 to establish an electrical circuit between one of the insulated conductors H8 and the metallic frame of the instrument. This condition may be (indicated by connecting the said one of the conductors H8 and the frame of the instrument in series with a lamp or other indicating device, which may be conveniently located for that purpose, and which is not shown herein in order to avoid unnecessary complication of the drawings. When the desired movement of the film I30 has been eifected, the contact finger H again engages the insulating insert I2I in the disc I20 and interrupts the indicating circuit, it being understood that the contact finger I I9 is other wise suitably insulated from the framework or casing of the instrument. Upon extinguishment of the lamp or corresponding indication of any other indicating device that may be utilized, the operator is informed that the film has been moved through the desired distance and that a fresh portion thereof is ready for exposure. It is also contemplated that the contact mechanism comprising the finger H0 and the disc I20 having the insulating insert I2I therein may be utilized to effect automatic operation of the film by an electric motor or other suitable means in response to any desired condition indicating that a record has been made on the exposed portion of the film and that a fresh portion of the film should be brought into the field of exposure. The essential element of this feature of the invention, however, is in associating the indicating, mechanism comprising the disc I20 with an idler roll, such as the roll I32, that is rotated through a predetermined degree for any given movement of the film I30, while the degree of rotative movement of the winding rolls I20 and I29 is variable depending upon their effective circumferences, that is, depending upon the amount of film which has been wound from one of these rolls onto the other.

For the purpose of permitting visual inspection of the movements of the cathode ray or beam I under the influence of the phenomena being observed, a phosphorescent or fluorescent screen I02 is hinged about ahorizcntal axis at I63 to a fixed portion of the frame I22 of the film mech-' anism. This screen is adapted to be rotated about the axis I43 between the full line and dotted line positions indicated in Fig. 9. In the dotted line position, as shown in this figure, the screen is entirely out of the .path of the cathode ray orbeam, ,which therefore impinges on the film I30 and is photographically recorded thereon. When the screen I02 occupies the position indicated in full lines in Figs. 8 and 9, it is horizontally disposed above the exposed portion of the film I30 in the path of the cathode ray or beam, and the upper surface thereof may be viewed through a glass window I66 that is provided near the outer extremity of the tubular member 07, as indicated in Fig. 8. The window I66 is tightly sealed in the outer end of the tubular member It! ;by

means of suitable gaskets I 65 and a flanged securing sleeve I06 that is internally screw-threaded to cooperate with corresponding external screw threads at the outer extremity of the tubular member 07'. The outer surface of the flanged sleeve I66 is suitably hour, as indicated at I61,

whereby it may be tightly screwed onto the end cf'the member 0? to form a ectly air-tight aoeasae connection between said member 61 and the window I60. The member 41 is suitably fixed to a side wall of the tapered casing portion 03 in register with an aperture therein by means of soldering or brazing to form an air-tight connection at this point.

It will be seen from an examination of Fig. 8 that the viewing screen I42 may be clearly viewed through the window I40 when said screen is in its operative position as shown. The screen or the mounting plate therefor also serves in this position as a light-proof shutter to protect the film I60 from exposure to light entering the casing through the window I40. It will be understood, of course, that the cap or cover 07a previously mentioned with reference to Figs. 1 and 2 is used to cover the window it when the movements of the cathode ray or beam are being recorded on the film I30 instead of being viewed on the screen I42. This cap or cover prevents the entrance of light into the film chamber through the window I60, which light might affect the sensitized film I 30. The provision of such a cap may not be necessary; however, where the window I60 is composed ofv colored glass which will not admit any light that will affect the film I30, but which will permit the observation of the path of movement of the cathode ray or beam as indicated on the screen I42.

The screen I62 is adapted to be actuated be tween its operative and inoperative positions by means of a pin I58 extending through an airtight sealing gland I09 in the end wall N3 of the film chamber 22, as shown in Fig. 1. The outer extremity of the pin I 60 is provided with an operating handle I50, and the inner extremity of this pin is adapted to engage the axial portion I03 of the screen I02 in a suitable operative manner. Thus, the instrument may be adapted either for visual observation or for photographic recording of the movements of the cathode ray or beam by simply manipulating the handle I50 on the outside of the casing. It will be understood that the screen I02 is so mounted that it will remain in either of its two positions when it has been actuated into such position by the manipu- I lation of the handle I50.

The enlarged view of Fig. 12 diagrammatically indicates the manner in which the cathode ray or beam is emitted from the filament It and electrcstatically focused. In this figure the lines II indicate the electron emission from the filament It, the electrons thus emitted passing through the relatively large central aperture 18a in the member I8 of the filament shield. An electrostatic field indicated by the lines I52 is created between the member I8 and the member which constitutes the top of the negative electrode 09. This electrostatic field I52 is created by applying a suitable potential difference between the filament shield 63 and the negative electrode 69. This potential difierence may be of any desired magnitude, but it has been found that a potential difierence of between 100 and 2,000 volts produces the most satisfactory results. The negative electrode 69 is positively energized with respect to the filament shield 63 by means of this potential difference, the member 69 being designated as the negative electrode because it is negatively energized with respect to the positive electrode 80, as will hereinafter appear.

The electrostatic field I 52 exerts a focusing and accelerating effect upon the cathode ray or beam between the filament shield and the top of the negative electrode 69 and the ray or beam is thus caused to be projected downwardly through the central aperture a, where it is brought to a focus, into the interior of the bell-shaped member 69. The stray or unfocused electrons which pass through the aperture 18a in the bottom of the filament shield are intercepted by the member Hi, the aperture 10a therein being of such size as to permit only a relatively thin pencil of focused rays to pass therethro-ugh.

The negative electrode 69 and the positive electrode 80 are respectively connected to the nega-,

tive and positive sides of a suitable source of potential difference to create an electrostatic field between these members, as indicated by the lines I53. The magnitude of this potential difierence may be varied between relatively wide limits, it having been found in actual practice that potentials varying anywhere between 3.00 and 20,000 volts produce satisfactory results. It will be understood, of course, that the invention is not limited to the use of any particular potential difference or range of potential differences as applied to these or any other portions of the instrument, the figures given being stated merely by way of examples.

Due to the telescoped relation of the electrodes 69 and 80, the electrostatic field I53 is caused to converge downwardly toward the positive electrode 80, as indicated by the inclination or curvature of these lines in Fig. 12. The utilization of the electrodes 69 and 80 in the relation disclosed is an important feature of the invention because it hasbeen found that a converging field of this character exerts a strong focusing effect upon the cathode ray or beam, which is diagrammatically indicated by the lines I54. The electrons in the beam- I54 start to diverge as indicated after passing through the focus at the aperture 10a and they also exert a mutually repelling effect by reason of their similar negative charges. This repelling effect would normally cause the beam to be substantially dispersed in the relatively long path of travel of the electrons. However, by utilizing the converging electrostatic field I53, as disclosed, this dispersive effect is entirely overcome, and the cathode beam I54 is accurately focused upon the film I30 or the viewing screen I42. This effect is obtained because the radiaI component of the field I53-imparts to the elec- .trons constituting the cathode ray or beam a component of velocity toward the center of the beam, which radial component of velocity counteracts the dispersive momentum of the electrons caused by their mutual repelling forces during the entire length of the beam..

The extent of the focusing effect required under different operating conditions may vary considerably, and it is for this reason that the positive electrode 80 is provided with adjusting means operable by the knurled knob 88, as shown in Fig.7 and previously described. By adjusting the knob 88 the positive electrode 80 may be raised or lowered a substantial distance to effect the exact degree of convergence of the electrostatic field I53 which will effect the necessary focusing eifect upon the beam I54. This will be apparent from a consideration of the structure disclosed,

since a raising of the positive electrode 80 will obviously effect such a change in the inclination of-the lines of the electrostatic field I53 that the degree of convergence of these lines will be increased, and vice versa.

The focusing effect of the electrostatic field I53 may also be varied by changing the magnitude of the potential difference applied between the electrodes I8 and 10, but the degree of variation obtained by the adjustable mounting of the positive electrode 80 is such as to give a wide range of variation by this means alone, whereby it is not ordinarily necessary to change the magnitude of the voltage applied to the electrodes I8 and 10- for ordinary variations in the conditions under which the instrument is operated.

It will also be understood that the electrostatic field I53 exerts an accelerating effect upon the cathode ray or beam I54 whereby the desired velocity of this beam is obtained. The magnitude of this accelerating effect may be readily varied by varying the potential difierence that is applied between the electrodes 69 and 80, so that any desired velocity of the beam may be obtained for any given operative conditions. ing of the electrodes 69 and 80 and the magnitude of the potential difference that is utilized therebetween may be adjusted so that both the focusing effect and accelerating effect of the field I53 may be adjusted to the proper values. With this construction, the focusing of the beam may be readily accomplished regardless of the gas pressure within the instrument, as long as this pressure is not above the necessary minimum value of, say, a few one-hundredths of a millimeter.

The method of focusing'a cathode ray or beam by the use of high-voltage electrodes in adjustable telescoped relation is believed to be entirely new and is broadly claimed herein, since this method may be utilized wherever a cathode ray or beam is to be focused for any purpose, such as in a television system or elsewhere.

The beam I54, after passing through the electrostatic field I53 between the electrodes 69 and 80, passes through the central aperture 8Ib in the cap member 8| at the top of the positive electrode 80, and thence continues downwardly through the interior of the electrode 80, which is made hollow for this purpose. The aperture 8Ib is of suflicient size to permit the entire beam to pass therethrough and the inclination of the walls of said aperture is such as to prevent the electrons from striking said walls, thereby eliminating undesirable conditions, particularly heating of the members 8| and 80.

As the beam I54 continues along its downward path of travel within the positive electrode 80, any stray electrons which may be liberated from the beam are intercepted by the walls of the member 80 and are thus prevented from bombarding the interior of the insulating casing portion 25. This feature is of considerable importance because it has been heretofore considered necessary to construct such a casing portion of glass or similar material in order to withstand the high temperature caused by such stray electron bombardment. Such bombardment in instruments heretofore devised has been very considerable because widely separated electrodes establishing an accelerating field with substantially parallel lines of force have been utilized almost universally, with the result that the cathode beam diverges substantially between the cathode and anode. The use of a converging field produced by closely spaced telescoped electrodes substantially eliminates this condition in instruments constructed in accordance with the present invention, thus permitting the casing portion 25 to be made of any desired insulating material, molded or otherwise, such, for example, as phenol condensation products or the like. "Such products are capable of being accurately machined and molded so that the dimculties incident to the proper construction of the Thus, the spacinstrument are greatly reduced. Moreover, the member protects the beams from surface charges on the inside of the casing portion 35, and thus prevents "fiickering of the beam which might otherwise be caused by such charges.

When the beam I54 reaches the bottom of the space enclosed by thepositive electrode 80 and the supporting sleeve 82 therefor, it passes through the aperture I021 in the plate 102, shown in Fig. 7. This plate intercepts the few stray electrons which may have been thrown off from the main beam I56, but substantially all of the electrons in the beam are accurately maintained in focus by reason of the above-described action of the electrostatic field I53, and the entire beam thus focused passes freely through the aperture I02a. inclined as shown-so that in case the beam is not properly centered through said aperture it will not be thrown out of focus by reason of the glancing or reflection of electrons from these walls.

The cathode ray or beam then passes between the two pairs of deflecting plates and 9|, and thence downwardly through the casing portion 23 to impinge upon the viewing screen I62 or the exposed portion of the film I30. An oscillating potential difference of known frequency, or a varying potential difference of which the rate of change is known or can be determined, is connected between the two plates of one of the pairs of plates 90 and 9| to cause the cathode ray or beam to be periodically oscillated or to produce a time axis or datum. Such a timing potential difference may be derived from a vacuum tube circuit, which is advantageous because it is possible thereby to apply a straight-line timing motion automatically, or may be obtained in any other suitable manner well known in the art. The two plates of the other pair of the deflecting plates 90 and 9I are connected to the circuit in which the phenomena to be observed or recorded obtain, and thus the cathode ray or beam is deflected by such phenomena in a direction perpendicular tothat in which it is deflected by the timing potential diiference that is connected to the other pair of plates. In this manneran indication on the screen I42 or a record on the film I30 is produced to indicate the exact nature of the phenomena under consideration.

The instrument is also adapted for the use of electro-magnetic means for deflecting the beam, which means are known in the art and generally comprise magnetic coils wound upon hollow cylindrical members of insulating material. Such a member may be secured, if desired, between the parts I06 and I05 of the instrument casing where by the beam may be deflected magnetically instead of, or as well as, electrostatically. Such magnetic deflecting means are not ordinarily required, but may be useful for laboratory work.

The focusing effect of the electrostatic field I53 is so adjusted that the dispersive tendency of the electrons in the cathode ray or beam is counteracted to a sufiicient extent to concentrate the electrons throughout the entire path of their travel and bring them to an accurate focus upon the screen I 42 or film I30. Thus, the beam produces a well defined spot of high intensity on the screen or film whereby the movements of the beam are accurately reproduced thereon. In this connection it may be stated that the oxide coating on the bottom of the filament 16, and the small size of the aperture 10a, substantially eliminate all light emission from sa d fi ament in a The side walls of the aperture I02a are downward direction through the several small apertures in the path of travel of the cathode ray or beam and therefore there is insufhcient light reaching the film I 30 from the filament It to have any effect upon said film except for very long exposures thereof.

The circuit diagrams shown in Figs. 13 and 14 will now be described to illustrate an application to which an instrument constructed in accordance with the present invention is particularly adapted.

In Fig. 13 the filament 14 is shown as being connected through its lead wires and the conductor rods 5I to conductors I55 and I56, the former of which is connected through an ammeter I51 to a conductor I58 which extends to a suitable source of current (not shown) for heating the filament. The conductor I56 is preferably connected through a variable resistor I59 to a conductor I60 which extends to the other side of the source of filament current supply. The amount of current traversing the filament 14 may thus be varied by adjusting the effective value of the resistor I59, and is indicated to the operator by the ammeter I51.

The filament shield 63 is diagrammatically illustrated as being connected to one side of the filament 10, and the same side of the filament is connected through a conductor I6I to the plates I62 of two triode electron tubes I63 which are preferably of the high vacuum type. The filaments I 66 of the tubes I63 are connected in parallel with each other and are adapted to be energized from a suitable source of current (not shown) through two supply conductors I65, one of which is connected through a conductor I66 to the negative side of a source of direct current potential that is to be applied to the filament I0 and the shield 63 on the one hand, and the cathode 69 on the other hand. The positive side of this potential source, which, as is indicated on the drawings, may suitably have a value of to 2,000 volts, is connected through a conductor I61 to the negative electrode 69. The conductor I61 is also adapted to connect the negative electrode 69 to the negative side of a source of relatively high direct current potential, which, for example, may be of a suitable value between 100 and 30,000 volts, as indicated on the drawings. The positive side of this high potential source is connected through a conductor I 68 to the positive electrode 80 of the oscillograph, and is also preferably grounded, as indicated at I69.

The connection from the conductor I61 to the negative electrode 69 is made by means of a binding post or screw I10, which, as indicated in Figs. 1, 2 and 3, is suitably mounted on the metal casing portion 21, the lower extremity of which is in electrical contact with the negative electrode 69. The conductor I68 may be secured to any convenient point on the metallic portions of the casing of the instrument below the insulating portion 25, as, for example, to a binding post or screw III on the side of the metallic casing portion 24, as indicated in Fig. 7. The exact location of such a binding post or screw is immaterial because all of the portions of the casing below the insulating portion 25 are of metal and are in contact with each other, except on comparatively rare occasions when an insulating tubular section carrying a beam-deflecting eiectromagnet is secured between the parts I06 and I05 of the casing as above mentioned. In view of this fact the grounding of the conductor I68, as indicated at I69 in Fig. 13, is'a material factor of safety for the operator, because none of the portions of the casing is electrically energized above ground potential except the upper casing portion 21, which is protected by the four insulating rod portions 32b.

One of the deflecting plates 90 is connected through a conductor I12 to a timing oscillator or other suitable source of timing potential, one form of which is described hereinafter, and the other of this pair of plates is connected through a conductor I13 to grcund, to which the other side of the timing circuit will also be connected. In this manner a suitable timing potential is applied to this pair of deflecting plates, as previously described. One of the pair of deflecting plates 9| is connected through a conductor I14 to ground, while the other of this pair of plates is connected through a conductor I15 to an antenna I16 that is suitably suspended between a high-potential transmission line I11, or other conductor that is to be subjected to the phenomena under observation, and a grounded counterpoise I18. In this manner the antenna I16 is subjected to the lightning surges or other abnormal conditions occurring on the line I 11 without being directly connected to said line, by reason of the disposition of the antenna in the electrostatic field between the line I11 and the counterpoise I18. If desired, the antenna I16 and counterpoise I18 may be replaced by a dividing condenser to accomplish the same result. Accordingly, an electrostatic field of varying intensity depending upon the conditions obtaining in the line I11 is created between the two deflecting plates 9|. The conductor I15, antenna I16 and the plate 9I to which the conductor I15 is connected, are preferably grounded through a resistor I19 of the magnitude of 5,000,000 to 10,000,000 ohms to prevent the accumulation of an excessive static charge in'this portion of the circuit.

A resistor I of suitable resistance value is connected in parallel relation to the filaments I64 of the two vacuum tubes I 63, and an intermediate point on this resistor is connected through a conductor I8I to the positive terminal of a grid-biasing battery or C battery I82. The negative terminal of the battery I82 is connected to a conductor I83 extending between one terminal of each of two secondary windings I84 of a transformer I85, which is preferably of the air core type. This transformer further comprises a primary winding I86 having one of its terminals connected to ground through a conductor I81, and having its other terminal con nected through a conductor I88 to a second antenna I89 that is disposed similarly to the antenna I16 between the high voltage line I11 and the grounded counterpoise I18. The outside term nals of the secondary windings I84 of the transformer I are respectively connected through conductors I to the grids I9I of thev vacuum tubes I63.

With the above described connections, the grids I9I of the vacuum tubes I63 are normally negatively biased with respect to the filaments I64 by the C battery I82, this negative bias being transmitted through the conductor I83, the secondary windings I84 of the transformer I85 and the conductors I90 to the respective grids I9I, while the positive side of the battery is connected to the filaments I64 through the conductor I8I and the balancing resistor I80. By reason of this negative grid bias in the tubes I63, the potential between the conductors I66 and I61, which must be applied to the filament 14, or its shield 63, and the negative electrode 69 to establish the cathode ray or beam I54 in the oscillograph, is cut off from the instrument because no current can flow between the conductors I6I and I66 while the grids I9I of the vacuum tubes I63 are properly or sufliciently negatively biased with respect to the filaments I64 of these tubes.

Since the beam voltage supplied through the conductors I66 and I61 is thus effectively cut oil from the oscillograph by the valve action of the tubes I63, the filament 14 of the oscillograph may be continuously maintained in a heated condition and the relatively high voltage between the conductors I61 and I68, which are respectively connected to the negative electrode 69 and the positive electrode 80 to establish an accelerating and focusing electrostatic field therebetween, may be continuously connected to these electrodes so that this field is continuously maintained. The timing potential circuit, of course, may also be continuously connected across the deflecting plates 90 without having any effect upon the instrument, and the fllm I30 or viewing screen I42 may be maintained in operative position to record or indicate the deflections of the cathode ray or beam I54 as soon as the same is established and as long as it is maintained.

Therefore, all that it is necessary to do to place the oscillograph in operation for recording or observation of the phenomena occurring on the line I11 is to apply the proper voltage between the filament 14, or its shield 63, and the negative electrode 69. This is accomplished by means of the circuits through the vacuum tubes I63 because the negative bias on either or both of the grids I9I is overcome by the potential induced in 'the secondary circuits of the transformer I85 upon the occurrence of a surge in the line I11, which causes current to traverse the primary winding I86 of this transformer because this primary winding is connected between the antenna I 89, disposed adjacent the line I11, and ground. The time required for establishment of the beam voltage between the filament 14, or its shield 63, and the negative electrode 69 is negligible with this arrangement and is only that required for electrostatically charging the circuit portions between which the potential is to be applied. The instrument and related circuits are so designed that their electrical capacity is ex tremely small, and it has been found in actual practice that the time required for building up the voltage for initiating the beam is not over one-half of one one-millionth of a second and may be as small as a quarter of one one-millionth of a second. It will be readily appreciated that this amount of delay in bringing the instrument into operation is negligible in practice and will not eifect a loss of any appreciable portion of the wave front of the phenomena to be recorded, even though these phenomena are of extremely short duration, as in the case of surges caused by lightning.

When the beam voltage is applied to the oscillograph in the manner described, the cathode ray or beam I54 is immediately established and is'accelerated downwardly through the electrostatic field between the negative electrode 69 and the positive electrode 80, and thence downwardly between the two pairs of deflecting plates 90 and 9| to impinge upon the'film I30 or the screen I42. The timing potential applied between the plates 90 causes the beam to be deflected transversely of the film or viewing screen and the electrical characteristic or phenomenon that is to be insulated conductor recorded or observed creates a varying electrostatic field between the two deflecting plates 9I whereby the beam is deflected in a direction normal to the direction of the timing deflection of the beam. A record or indication of the nature and extent of the phenomenon is thus accurately produced upon the film or viewing screen.

The beam is maintained as long as the initiating potential therefor is connected between the filament I I, or its shield 63, and the negative electrode 69, and this potential is applied to these portions of the instrument until bothof the grids I9I of the two vacuum tubes 63 are again fully or properly negatively biased with respect to the filaments I64, since the two transformer secondary windings I89 are of opposite polarity with respect to each other" to permit the establishment of the oscillograph potential circuit in response to the occurrence of a surge of either polarity with respect to the ground.

When the surge is terminated, the primary winding I86 of the transformer I is no longer traversed by current and the C battery I82 therefore again becomes effective to apply its negative bias to the grids I9I of the two vacuum tubes I63. Thus, the potential between the conductors I66 and I 61 is cut off from the oscillograph just as soon as the surge or other phenomenon to be recorded or observed has terminated.

Another method whereby the oscillograph may be placed in operative condition in response to the occurrence of the phenomena to be recorded or observed is illustrated in Fig. 14, in which .the several parts of the apparatus represented that are identical with parts illustrated in Fig. 13 are designated by the same reference characters that are applied to the corresponding parts in Fig. 13.

Referring to Fig. 14, it will be seen that the filament M is energized from a suitable supply of current through conductors I55, I56, I58 and I66 and the ammeter I51 and variable resistor I59 exactly as shown in Fig. 13. The filamentshield 63, however, is not directly connected to either side of the filament I9, but is insulated from said filament in a manner heretofore referred to. This resiL t is accomplished in the construction of the oscillograph simply by extending three of the conducting rods 5| through the insulating cap 29 of the oscillograph casing instead of utilizing only two such rods, as indicated in Fig. 4. One of the three rods 5| is connected to the filament shield 63 through the metallic sleeve mem-' ber 62 exactly as indicated in Fig. 4, and the filament, lead I6 is connected to another one of the rods 51 through the insulated conductor 59 as also shown in this figure. The other filament lead 15, however, instead of being connected to the metallic sleeve 62, is connected through a second similar to the conductor 59 to'the third will be very readily understood.

With the filament I6 and its shield 63 thus insulated from each other, it becomes possible to apply a negative bias to the shield with respect to the filament, and this is done by means of the vacuum tubes I63 in a manner similar to that in which these tubes interrupt the circuit between the conductors I6I and I66 in Fig. 13. One side of the filament I6 is connected through the corresponding conducting rod 5I and a conductor I92 to the positive terminal of a battery I93, the negative terminal of which is connected through two branches of a conductor I98 to the plates I62 of insulated rod 5| in a manner which.

the vacuum tubes I63. The conductor I96 is also connected to one end of a resistor I95, the other end of which is connected to the positive terminal of a second battery I96 and also, through a conductor I91, to the filament shield 63. The negative terminal of the battery I96 is connected through a conductor I98 to one side of the filaments I64 of the two tubes I63. A condenser I99 is connected in parallel with the battery I96 for the purpose of by-passing any inductance which may exist in the internal connections of said battery, thereby hastening the building up of current in the tube circuits after a positive impulse has been received by the grids.

The filaments I64 are energized as in the system illustrated in Fig. 13 through the conductors I65 extending to any suitable source of filament current supply, and all of the remaining parts of the system, including the resistor I86, the battery I32, the primary and secondary windings of the transformer I85, the grids I9I of the vacuum tubes I63, the antenna I89, the electrodes 69 and 86 and the deflecting plates 96 and 9| of the oscillograph, are connected in exactly the same manner as shown in Fig. 13, and, therefore, the conductors for establishing these connections are indicated by the same reference characters as in Fig. 13.

It is to be noted, however, that the voltage between the filament shield 63 and the negative electrode 69 is continuously connected to these elements by means of the conductors I 61 and I91, rather than being connected through the vacuum tubes I63, since these vacuum tubes are now utilized to establish the cathode ray or beam in the oscillograph without interrupting the circuit by which this beam voltage is applied to the oscillograph. This is accomplished by normally maintianing the filament I4 at a positive potential with respect to the shield 63 (which includes the member 18). This positive potential is maintained by the battery I93, the positive terminal 0 which is connected directly to the filament I through the conductor I92 and the negative terminal of which is connected to the member 63 through the resistor I95 and the conductor I 91. When a surge, or similar phenomenon to be observed or recorded, occurs on the line In, the resultant positive energization of either or both of the grids of the tubes I63 permits current from the battery I96 and condenser I99 to traverse the resistor I95. This establishes a potential drop across the resistor I95 in opposition to the potential of the battery I93. In this manner the potential between the filament I4 and its shield 63 may be brought to zero, or, if desired, may be overbalanced to make the shield positive with respect to the filament, with the result in either case that electrons from the filament are immediately permitted to pass through the opening 18a in the shield and to establish the beam for operating the instrument.

In a system such as those shown in Figs. 13 and 14, the vacuum tubes I63 are effective to prevent the establishment of the cathode ray or beam except upon the occurrence of the abnormal conditions or phenomena on the line I" which it is desired to record or observe. The antenna I89 may be designated as a controlling antenna, since it controls the effectiveness of the vacuum tubes I63 and through the instrumentality of these tubes causes the cathode ray or beam to be established and maintained in the oscillograph only during the occurrence of the said abnormal con- 

